Publications of NIPGR Scientists

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Author: search.filters.author.Pathak, Pradeep KumarSubject: search.filters.subject.nitrate reductase

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    The emerging roles of nitric oxide and its associated scavengers-phytoglobins-in plant symbiotic interactions
    (Oxford University Press, 2024) Pathak, Pradeep Kumar; Yadav, Nidhi; Kaladhar, Vemula Chandra; Jaiswal, Rekha; Kumari, Aprajita; Igamberdiev, Abir U.; Loake, Gary J.; Gupta, Kapuganti Jagadis
    A key feature in the establishment of symbiosis between plants and microbes is the maintenance of the balance between the production of the small redox-related molecule, nitric oxide (NO), and its cognate scavenging pathways. During the establishment of symbiosis, a transition from a normoxic to a microoxic environment often takes place, triggering the production of NO from nitrite via a reductive production pathway. Plant hemoglobins [phytoglobins (Phytogbs)] are a central tenant of NO scavenging, with NO homeostasis maintained via the Phytogb–NO cycle. While the first plant hemoglobin (leghemoglobin), associated with the symbiotic relationship between leguminous plants and bacterial Rhizobium species, was discovered in 1939, most other plant hemoglobins, identified only in the 1990s, were considered as non-symbiotic. From recent studies, it is becoming evident that the role of Phytogbs1 in the establishment and maintenance of plant–bacterial and plant–fungal symbiosis is also essential in roots. Consequently, the division of plant hemoglobins into symbiotic and non-symbiotic groups becomes less justified. While the main function of Phytogbs1 is related to the regulation of NO levels, participation of these proteins in the establishment of symbiotic relationships between plants and microorganisms represents another important dimension among the other processes in which these key redox-regulatory proteins play a central role.
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    Alternative oxidase is an important player in the regulation of nitric oxide levels under normoxic and hypoxic conditions in plants
    (Oxford University Press, 2019) Kumari, Aprajita; Pathak, Pradeep Kumar; Bulle, Mallesham; Igamberdiev, Abir U; Gupta, Kapuganti Jagadis
    Plant mitochondria possess two different pathways for electron transport from ubiquinol: the cytochrome pathway and the alternative oxidase (AOX) pathway. The AOX pathway plays an important role in stress tolerance and is induced by various metabolites and signals. Previously, several lines of evidence suggested that the AOX pathway prevents overproduction of superoxide and other reactive oxygen species. More recent evidence suggests that AOX also plays a role in regulation of nitric oxide (NO) production and signalling. The AOX pathway is induced under low phosphate, hypoxia, pathogen infections and elicitor treatments. The induction of AOX under aerobic conditions in response to various stresses can reduce electron transfer through complexes III and IV and thus prevents the leakage of electrons to nitrite and the subsequent accumulation of NO. Excess of NO under various stresses can inhibit complex IV, thus the AOX pathway minimizes nitrite-dependent NO synthesis that would arise from enhanced electron leakage in the cytochrome pathway. By preventing NO generation, AOX can reduce peroxynitrite formation and tyrosine nitration. In contrast to its function under normoxia, AOX has a specific role under hypoxia, where AOX can facilitate nitrite-dependent NO production. This reaction drives the phytoglobin-NO cycle to increase energy efficiency under hypoxia.
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    Pathways of nitric oxide metabolism and operation of phytoglobins in legume nodules: missing links and future directions
    (John Wiley & Sons, 2018) Berger, Antoine; Brouquisse, Renaud; Pathak, Pradeep Kumar; Hichri, Imène; Singh, Inderjit; Bhatia, Sabhyata; Boscari, Alexandre; Igamberdiev, Abir U.; Gupta, Kapuganti Jagadis
    The interaction between legumes and rhizobia leads to the establishment of a beneficial symbiotic relationship. Recent advances in legume - rhizobium symbiosis revealed that various reactive oxygen and nitrogen species including nitric oxide (NO) play important roles during this process. Nodule development occurs with a transition from a normoxic environment during the establishment of symbiosis to a microoxic environment in functional nodules. Such oxygen dynamics are required for activation and repression of various NO production and scavenging pathways. Both the plant and bacterial partners participate in the synthesis and degradation of NO. However, the pathways of NO production and degradation as well as their cross-talk and involvement in the metabolism are still a matter of debate. The plant-originated reductive pathways are known to contribute to the NO production in nodules under hypoxic conditions. Non-symbiotic hemoglobin (phytoglobin) (Pgb) possesses high NO oxygenation capacity, buffers and scavenges NO. Its operation, through a respiratory cycle called Pgb-NO cycle, leads to the maintenance of redox and energy balance in nodules. The role of Pgb/NO cycle under fluctuating NO production from soil needs further investigation for complete understanding of NO regulatory mechanism governing nodule development to attain optimal food security under changing environment.